1. Field Of The Invention
This invention lies in the field of plasma emission spectroscopy, and more particularly relates to improved methods and apparatus for sample aerosol production.
2. Prior Art
In prior art inductively coupled plasma emission spectroscopy, a sample of a substance being analyzed is dissolved in a solvent, and the solution in a controlled chamber is converted by a nebulizer system into an aerosol. The aerosol in a uniform manner is conveyed into a plasma zone from which light signals are emitted that are representative of the substance being analyzed. The procedure can be derived from, for example, the Perkin-Elmer Informationsheft 28, pp. 15-17 (1981).
In the evaluation of the light signals emitted from the plasma after introduction thereinto of aerosol, in simultaneous spectrometry, a relatively small sample solution volume suffices because the optical information of all elements contained therein is simultaneously registered. It is thereby possible to execute multi-element analyses from small solution volumes having high element concentration and to obtain favorable element detection limits. The known disadvantage of the simultaneous spectrometer with photoelectric evaluation is the limitation of the scope of use to analysis lines preliminarily selected.
This disadvantage is avoided in sequential spectrometry in that the analysis lines in the spectrometer, being matched to the respective problem, can also be freely selected and with constant variation. This freedom is acquired at the expense of a higher sample consumption because the analysis lines must be successively selected, and, thus, the emitted light signals from the plasma can likewise not be simultaneously, but only sequentially, recorded. The higher sample consumption therefore requires a greater sample dilution, and, particularly in quantitative multi-element analyses, results in a deterioration of the detection limits of the particular elements being analyzed.
The known nebulizer system for producing an aerosol is described, for example, in an article by G. F. Wallace et al from Paper No. 157 of the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Atlantic City, N.J., Mar. 8-12, 1982. In such system, only about 10% of the sample amount employed is introduced into the plasma, while, in contrast, about 90% is discharged from a spray chamber unused.